1. Field of the invention:
This invention relates to a high-performance semiconductor device attaining the quantum effect of one dimension, such as light-emitting diodes, semiconductor lasers, electric field effect transistors, etc.
2. Description of the prior art:
In recent years, an epitaxial growth technique for the formation of thin films such as molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MO-CVD), etc., has been developed which enables the formation of thin film epitaxial growth layers having a thickness of as thin as approximately 10 .ANG. or less that is the order of a single molecular layer. The development of such an epitaxial growth technique, although these significantly thin films have not yet been produced by liquid phase epitaxy (LPE), allowed a device structure with the thin films to be applied to laser devices, resulting in semiconductor laser devices utilizing the quantum effect. These semiconductor devices are produced by the formation of a device structure on the (100) plane of a substrate in which the thin films are disposed in the &lt;100&gt; direction that is vertical to the (100) plane so that the quantum effect of one dimension arises in the &lt;100&gt; direction. These semiconductor devices utilize the said quantum effect of one dimension. A typical example of these semiconductor devices is a GaAs/AlGaAs quantum well (QW) laser, the production of which is based on the fact that quantization levels are established in its active layer by reducing the thickness of the active layer from several hundred A to approximately 100 A or less and which is advantageous over conventional double-heterostructure lasers in that the threshold current level is lowered and the temperature and transient characgteristics are superior. Such a quantum well laser is described in detail in the following papers:
(1) W. T. Tsang, Applied Physics Letters, vol. 39, No. 10 pp. 786 (1981) PA1 (2) N. K. Dutta, Journal of Applied Physics, vol. 53, No. 11, pp. 7211 (1982), and
(3) H. Iwamura, T. Saku, T. Ishibashi, K. Otsuka, Y. Horikoshi, Electronics Letters, vol. 19, No. 5, pp. 780 (1983).
Another typical example of the abovementioned semiconductor devices is an electric field effect transistor (FET), which utilizes the moving characteristics of electronic gas of two dimensions that are produced at the interface between the GaAs layer and the AlGaAs layer (T. Mimura, et al, Japan. J. Appl. Phys. vol. 19, 1980, p. L225).
Moreover, other examples include a variety of devices using the electric field effect of excitons within the multi-layered quantum well, typical examples of which are an optical modulator and an optical logic device. These devices are designed to one-dimensionally confine electrons and positive holes within the quantum well layer having a thickness of about 200 .ANG. or less so that excitons can exist even at room temperature, and accordingly these devices attain operation characteristics utilizing the non-linear and linear properties of excitons (D. A. B. Miller et al: IEEE. Journal of Quantum Electronics, vol. QE-21, pp. 1462 (1985), S. Tarucha et al, Japanese Journal of Applied Physics, vol. 24, No. 6, pp. L442 (1985), K. Wakita et al, Surface Science vol. 174, pp. 233 (1986).
A variety of devices other than the abovementioned semiconductor devices have been studied which have a superlattice composed of alternate layers consisting of different semiconductor thin films with a thickness of several molecular layers and which utilize the quantum effect based on the periodicity of one dimension in the direction of the layer thickness of the said superlattice.
Since these semiconductor devices are produced on the (100) plane of a substrate, the quantum effect that is utilized in the said semiconductor devices is also based on the confinement of carrier in the &lt;100&gt; direction, the quantization in the &lt;100&gt; direction, and the periodicity in the &lt;100&gt; direction. On the other hand, it is well known that an electronic energy structure of semiconductor materials remarkably varies depending upon the crystal direction, and it is assumed that the quantum effect of one dimension will vary depending upon the crystal direction.